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Swelling Mechanisms of UO2 Lattices with Defect Ingrowths.

Günay SD - PLoS ONE (2015)

Bottom Line: In this study, experimental lattice expansion and lattice super saturation were accurately reproduced using a molecular dynamics simulation method.Moreover, in this work, defects are divided into two sub-groups, obstruction type defects and distortion type defects.Relative lattice expansion was found to vary linearly with the number of obstruction type uranium Frenkel defects.

View Article: PubMed Central - PubMed

Affiliation: Yıldız Technical University, Department of Physics, Faculty of Science, Esenler, Istanbul, Turkey.

ABSTRACT
The swelling that occurs in uranium dioxide as a result of radiation-induced defect ingrowth is not fully understood. Experimental and theoretical groups have attempted to explain this phenomenon with various complex theories. In this study, experimental lattice expansion and lattice super saturation were accurately reproduced using a molecular dynamics simulation method. Based on their resemblance to experimental data, the simulation results presented here show that fission induces only oxygen Frenkel pairs while alpha particle irradiation results in both oxygen and uranium Frenkel pair defects. Moreover, in this work, defects are divided into two sub-groups, obstruction type defects and distortion type defects. It is shown that obstruction type Frenkel pairs are responsible for both fission- and alpha-particle-induced lattice swelling. Relative lattice expansion was found to vary linearly with the number of obstruction type uranium Frenkel defects. Additionally, at high concentrations, some of the obstruction type uranium Frenkel pairs formed diatomic and triatomic structures with oxygen ions in their octahedral cages, increasing the slope of the linear dependence.

No MeSH data available.


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Relative lattice expansion versus number of obstruction type uranium defects, from Yakub and Günay potentials.
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pone.0134500.g010: Relative lattice expansion versus number of obstruction type uranium defects, from Yakub and Günay potentials.

Mentions: In Fig 10, lattice swelling clearly demonstrates a linear dependence on the number of obstruction type uranium defects for both potentials. This accounts for the lattice expansion observed during alpha particle irradiation. This was also observed in the 5×5×5 supercell, Fig 7(b), discussed in the preceding section and confirms the trend. Volume increments for obstruction type uranium FPs, as determined from Fig 10, are approximately 55.65 and 28.85 Å3 for the Yakub and Günay potentials, respectively. The value obtained from the Yakub potential is approximate because the slope of the plot in Fig 10 changes when the number of FPs exceeds 30. One possible reason for this is that obstruction type oxygen defects appear when more than 35–40 uranium IFPs, corresponding to 30 obstruction uranium FPs, are present, as seen in Fig 11.


Swelling Mechanisms of UO2 Lattices with Defect Ingrowths.

Günay SD - PLoS ONE (2015)

Relative lattice expansion versus number of obstruction type uranium defects, from Yakub and Günay potentials.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4526661&req=5

pone.0134500.g010: Relative lattice expansion versus number of obstruction type uranium defects, from Yakub and Günay potentials.
Mentions: In Fig 10, lattice swelling clearly demonstrates a linear dependence on the number of obstruction type uranium defects for both potentials. This accounts for the lattice expansion observed during alpha particle irradiation. This was also observed in the 5×5×5 supercell, Fig 7(b), discussed in the preceding section and confirms the trend. Volume increments for obstruction type uranium FPs, as determined from Fig 10, are approximately 55.65 and 28.85 Å3 for the Yakub and Günay potentials, respectively. The value obtained from the Yakub potential is approximate because the slope of the plot in Fig 10 changes when the number of FPs exceeds 30. One possible reason for this is that obstruction type oxygen defects appear when more than 35–40 uranium IFPs, corresponding to 30 obstruction uranium FPs, are present, as seen in Fig 11.

Bottom Line: In this study, experimental lattice expansion and lattice super saturation were accurately reproduced using a molecular dynamics simulation method.Moreover, in this work, defects are divided into two sub-groups, obstruction type defects and distortion type defects.Relative lattice expansion was found to vary linearly with the number of obstruction type uranium Frenkel defects.

View Article: PubMed Central - PubMed

Affiliation: Yıldız Technical University, Department of Physics, Faculty of Science, Esenler, Istanbul, Turkey.

ABSTRACT
The swelling that occurs in uranium dioxide as a result of radiation-induced defect ingrowth is not fully understood. Experimental and theoretical groups have attempted to explain this phenomenon with various complex theories. In this study, experimental lattice expansion and lattice super saturation were accurately reproduced using a molecular dynamics simulation method. Based on their resemblance to experimental data, the simulation results presented here show that fission induces only oxygen Frenkel pairs while alpha particle irradiation results in both oxygen and uranium Frenkel pair defects. Moreover, in this work, defects are divided into two sub-groups, obstruction type defects and distortion type defects. It is shown that obstruction type Frenkel pairs are responsible for both fission- and alpha-particle-induced lattice swelling. Relative lattice expansion was found to vary linearly with the number of obstruction type uranium Frenkel defects. Additionally, at high concentrations, some of the obstruction type uranium Frenkel pairs formed diatomic and triatomic structures with oxygen ions in their octahedral cages, increasing the slope of the linear dependence.

No MeSH data available.


Related in: MedlinePlus